Antidepressants stir cell growth

Reuters News Service

Published 5:30 am, Friday, August 8, 2003

WASHINGTON -- Anti-depressants may help stimulate the growth of new brain cells, U.S.-based scientists said Thursday in releasing research that may lead to the development of better drugs to fight depression.

Research on rats shows that two different classes of anti-depressants can help brain cells regenerate -- and not in areas normally thought of as being involved in depression.

The study fits in with others that suggest depression can shrink the hippocampus, a brain region crucial to learning and memory but only recently found to be involved in depression. Major stress and trauma -- both depression triggers -- can also cause the shrinkage.

New anti-depressants may be developed to target this process directly, said Rene Hen of Columbia University in New York, who led the study.

"The proof in humans is going to come when we extend the work into finding drugs that stimulate neurogenesis. If these drugs have anti-depressant effects in humans, this is going to be proof that the process is critical in humans," Hen said.

The new study may also help explain why it can take weeks for anti-depressants to give patients relief.

"If anti-depressants work by stimulating the production of new neurons, there's a built-in delay," said Hen. The stem cells that give rise to new cells need time to divide, to differentiate into neurons, move to their new homes and link up with other neurons.

To make sure that the new brain cells in the hippocampus were the source of the lifted depression, Hen and colleagues at Yale University and in France worked with genetically engineered mice, using X-rays to kill newly growing cells in the hippocampus.

These mice did not respond as they normally would to anti-depressants. Mice given fluoxetine, an anti-depressant sold under the brand name Prozac by Eli Lilly and Co., and then givenX-rays did not resume grooming as would be expected.

Mice who received no X-rays and were killed after being dosed for 11 or 28 days with fluoxetine showed significant growth of new brain cells.

A drug in a different class, the tricyclic imipramine, also stimulated the growth of neurons.